So it is a fusion type thing...
(It was never denied...
)
I would think that it would be because it would combine the powers of both people. I'm guessing that whoever starts the fusion remains dominant over the the two people?
If what I just guessed is true, then in the Kaze/Kenji fusion you brought up would be a good thing. Kaze, who, AFAWK, can only use Ki blasts would gain access to Kenji's powers. This would mean that Kaze would now temporally be able to use X-ray vision and an energy blade. He might also be able to use Kenji's Ki katana as well. And if he also borrows Kenji's mentality, he'd be able to use them effortlessly.
As to how long it'd last, only you'd know,
